Delta Air Lines announced on Sunday that is fixing a systems outage that has resulted in domestic flight departure delays.
The airline maintains that no flights in the air have been affected by the outage.
In a statement, the Federal Aviation Administration indicates that the grounding of Delta's domestic flights is due to "automation issues" and that international flights are exempt from the halt.
In an update at 11:45pm, the airline said around 150 flights were cancelled on Sunday, though not all cancellations are being reflected in Delta's systems including its website and mobile app.
The airline's CEO Ed Bastian admitted "this type of disruption is not acceptable."
The Delta system outage is its second in less than six months. In August, a systems outage forced the airline to cancel more than 1,800 flights and delay many more.
Delta explained in the ensuing days that a critical power control module at the airline's technology command centre malfunctioned, causing a surge to the transformer and a loss of power.
While power was stabilised and restored quickly, after the malfunction, Delta COO Gil West said in August that "critical systems and network equipment didn't switch over to backups", though "other systems did".
The systems that failed to switch over suffered from "instability", he added, affecting the performance of a customer service system used to process check-ins, conduct boarding, and dispatch aircraft.
Just last week, United Continental had to suspend domestic flights following a technical problem that lasted about two and a half hours. However, not many flights were affected.
Updated 3.00 pm EST 30 January 2017: Number of flights cancelled.